Novel phosphorus compounds



ire ties 3,060,008 NOVEL PHGSPHGRUS COMPDUNDS Hugo Stange, Princeton, N.J., assignor to FMC Corporation, a corporation of Delaware No Drawing. Filed Oct. 19, 1960, Ser. No. 63,467 Claims. (Cl. 44-69) This invention relates to novel phosphorus compounds and to spark ignition fuel compositions containing these compounds as engine deposit modifiers.

The use of tetraalkyl lead compounds to increase the octane rating of gasoline for spark ignition internal combustion engines has become widespread. However, during the combustion of gasolines containing these lead alkyl compounds, lead decomposition products are formed which deposit on the walls of the combustion chamber and on the spark plugs. These lead deposits introduce problems such as spark plug misfiring, spark knock, preignition, wild ping, and rumble. As a result of these problems, it has become common to add scavenging agents such as ethylene dichloride or ethylene dibromide to gasoline containing tetraalkyl lead anti-knock agents. These scavenging agents reduce the lead deposits by reacting with the lead to form volatile halides which can be eliminated through the exhaust. Although these agents are helpful in reducing the amount of lead deposit, they do not completely eliminate the deposits or the adverse effects thereof.

Recently, it has been found that certain phosphorus compounds are helpful in further decreasing the adverse effects of the lead deposits. However, there appears to be no correlation in properties between very closely allied compounds. One compound may be deficient in one property, while very often isomers and adjacent homologues are satisfactory as to this property and deficient in other respects. For one reason or another, none of the compounds heretofore proposed has been completely satisfactory. Among the adverse properties which are encountered are high cost of the compound, water solubility, gasoline insolubility, corrosiveness, and reduction in anti-knock effectiveness of the anti-knock agent.

The most important factor which has retarded the general use of phosphorus compounds is the increased cost of gasoline containing these compounds. At present the use of phosphorus compounds is restricted almost exclusively to premium and super-premium gasolines. There remains a need for relatively inexpensive phosphorus compounds having good gasoline additive properties.

It is an object of this invention to provide relatively inexpensive phosphorus compounds having superior properties as gasoline additives.

Another object is to provide improved spark ignition fuel compositions for internal combustion engines.

These and other objects will become apparent from the following description of this invention.

It has now been discovered that certain novel phosphorus compounds have superior properties as gasoline additives. The compounds of this invention are the normal, iso-, and secondary tris(dibutoxyphosphinylmethyl) phosphates having the formula These three isomeric compounds have the advantage of being relatively inexpensive, soluble in gasoline, and insoluble in water, as well as having unusual properties as engine deposit modifiers. They are particularly efiective in preventing abnormal combustion such as spark knock, preignition, and rumble. Moreover, these compounds do not significantly depress the anti-knock effectiveness of the anti-knock agent contained in the gasoline to which they are added. The superior properties of 3,056,98 Patented Oct. 23, 1962 these compounds are quite surprising in view of the fact that closely related compounds are not suitable as gasoline additives.

The tris(dibutoxyphosphinylmethyl) phosphates may be prepared in excellent yields by reacting phosphorus oxychloride with the corresponding dibutyl hydroxymethylphosphonates in the presence of an organic base. These phosphonates and their method of preparation are known. They may be prepared by reacting normal, iso-, or sec.- butanol with phosphorus trichloride to give the dibutyl ester of phosphorous acid. The dibutyl acid ester is then reacted with formaldehyde to form the dibutyl hydroxymethylphosphonate. The phosphonate cannot be prepared from tert.-butanol in this manner.

In reacting dibutyl hydroxymethylphosphonate with phosphorus oxychloride, about 3 moles of dibutyl hydroxymethylphosphonate and about 3 moles of organic base are reacted with each mole of phosphorus oxychloride. Preferably a slight stoichiometric excess of phosphonate and base is employed.

The organic base may be any organic compound which is a hydrogen chloride acceptor such as a tertiary amine. illustrative examples are heterocyclic amines such as pyridine and quinoline, dialkylanilines such as dimethylaniline and diethylaniline, trialkylarnines such as trimethylarnine and triethylamine, and many others.

The reaction is preferably carried out in the presence of a solvent in which the reactants and product are soluble, but in which the amine hydrochloride formed during the reaction is insoluble. The solvent should be inert toward phosphorus oxychloride. Illustrative examples of solvents are aliphatic hydrocarbons such as hexane or heptane, aromatic hydrocarbons such as benzene or toluene, and many others.

The temperature of the reaction may vary from room temperature to about C. The reaction should be cooled during the addition of the phosphorus oxychloride to prevent an undesirable temperature rise due to the exothermic heat of reaction. However, no special bene fits accrue from cooling below room temperature. The maximum temperature is generally governed by the reflux temperature of the solvent. Preferably, the reaction is carried out at 25-50 C. A substantial yield is generally produced within 2 hours, however longer periods of time increase the yields.

The amine hydrochloride may be removed from the reaction product by various means. A simple Washing step, a filtering step, or a combination of them may be used. The washing step may be carried out with water, or with an aqueous solution of NaOH saturated with NaCl. Preferably, a combination of these steps is employed. The solvent may be removed by a distillation step.

The tris(dibutoxyphosphinylmethyl) phosphates may also be prepared by the reaction of phosphorus oxychloride, formaldehyde, and the corresponding tributylphosphites. Paraformaldehyde is depolymerized by heating to a temperature above C., and the resulting monomeric gas is bubbled into a mixture of phosphorus oxychloride and tributylphosphite. The reaction takes place at temperatures between room temperature and 70 C;

fying the lead deposits resulting from the previous use of leaded gasoline. Preferably, however, the gasoline contains a tetraalkyl lead anti-knock agent such as tetramethyi lead or tetraethyl lead. I

e phosphate maybe added in an amount sufficient to reduce abnormal combustion. Amounts varying from about 0.0l-0.5 theory are suitable. A theory is defined as the amount of phosphorus that theoretically could convert all of the tetraalkyl lead to lead orthophosphate. Thus, a theory contains two atoms of phosphorus for every three atoms of lead present. Other additives such as scavenging agents, anti-rust agents, anti-oxidants, metal deactivators, induction system cleanliness agents, carburetor anti-icing agents, and dyes may be added, if desired. The following examples are given to further illustrate the novel compounds of this invention, and their preparation and use as gasoline additives. All parts and percentages are by weight unless otherwise indicated.

Example I A mixture of 15 parts of phosphorus oxychloride and 21 parts of benzene was added to a mixture of 100 parts of di-n-butyl hydroxymethylphosphonate, 85 parts of benzene, and 47 parts of triethylarnine. The temperature was kept below 40 C. during the addition and was then maintained at 20-30 C. for another 22 hours. The triethylamine hydrochloride was filtered, and the filtrate was washed with 100 parts of aqueous NaOH saturated with NaCl and then with 100 parts of water. The solvent was removed by stripping under vacuum. The yield was about 100% tris (di-n-butoxyphosphinylmethyl) phosphate, based on the phosphonate present.

Analysis.Calcu1ated for C27H60013P4I C, 45.2; H, 8.44- P, 173. Found: C, 44.4; H, 8.10; P, 17.4.

The above experiment was repeated following the above procedure except that the reaction was stopped after 5 hours. A yield of 83% was obtained.

In the same manner tris(diisobutoxyphosphinylmethyl) phosphate and t-ris(diasec.-butoxyphosphiny1methyl) phosphate were prepared using the corresponding dibutyl hydroxymethylphosphonates. Yields of about 100% were obtained.

Example 11 The eifect of tris(dibutoxyphcsphinyhnethyl) phosphates on the anti-knock characteristics of leaded gasoline was measured using the Research Method (ASTM designation: D909-59) and Motor Method (ASTM designation: D35759), the Motor Method being the more rigorous. The determinations were carried out by first measuring the octane number of a standard reference gasoline having an aromatic content of 17% and containing 3 ml. of tetr-aethyl lead per gallon. Three tenths theory of tris (dibutoxyphosphinylmethyl) phosphate was then added to a portion of the reference gasoline and the octane number was again measured. The anti-knock depression (AKD) of the phosphate additive was measured as the diiference between the octane number of the reference gasoline without the additive and the octane number of the same gasoline with the additive. Thus, the AKD values obtained are a measure of the reduction in octane number resulting from the addition of the phosphate. The data obtained are set forth in the following table:

The Research Method determination was repeated for tris(di n-butoxyphosphinylmethyl) phosphate using a reference gasoline having an aromatic content of 29%. The AKD was found to be,0.05. This value is quite surprising in view of the fact that AKDs generally increase with increases in aromatic content.

Example III This experiment was carried out to determine the value of tn's(di-n-butoxyphosphinylmethyl) phosphate as an engine deposit modifier. Tests were carried out using a stationary modified 1958 production model Oldsmobile Super 88 engine. The compression ratio was increased to 11.5: 1 in order to sensitize the engine to abnormal combustion characteristics. This engine was rated at 143 brake horsepower (Bl-LP.) at 2200 r.p.m. The engine was equipped with a 4-barrel carburetor, carburetor air cleaner, water pump, fuel pump, distributor, and coil. The generator was removed and, since a closed system heat exchanger was used, no fan was necessary. The engine power output was absorbed by a water-cooled eddy current dynamometer of 175 Hi. capacity. The engine was instrumented to measure engine speed, air-fuel ratio, fuel consumption, oil pressure, temperature, exhaust back pressure, and intake manifold vacuum.

A series of tests was run on the engine to determine the engine performance while in a clean condition. The engine was then operated continuously for hours with a high octane base fuel containing 3 ml. per gallon of tetraethyl lead (TEL) and no phosphorus additive at a speed of 2000 r.p.m. at a load of 37.5 B.H.P. and with the ignition timing set at 30 before top center (B.T.C.), which is conducive to deposit formation. After 100 hours of operation, the engine was stopped and the same series of tests was again carried out to determine engine performance.

The engine was cleaned and the above procedure was repeated using the same leaded base fuel containing 0.3 theory of tris(di-n-butoxyphosphinylmethyl) phosphate as an engine deposit modifier. The same series of tests was again carried out at zero and 100 hours of operation.

The following is a description of each of the tests:

Test fuel knock rating.The engine was operated at 1200 rpm. with the ignition timing set at 6 B.T.C. A measure of the anti-spark knock quality of the test fuel was obtained by determining the amount of throttle opening the engine would tolerate with audible trace intensity spark knock as the criterion. Data are reported as intake manifold vacuum in inches of mercury. A low manifold vacuum indicates a large throttle opening tolerance, which is desirable for optimum engine performance.

Surface ignition count.-The incidence of surface ignition was measured with the engine operating on a 100 octane reference fuel at 1200 r.p.m. with a full throttle and the ignition timing at 6 B.T.C. A surface ignition detector was used to count the relative number of ignitions which took place before the spark ignition as compared with a clean engine reference. The data are reported as the number of surface ignitionstnon-spark plug induced pressure pulses) per 1000 spark firings. Low values indicate a low incidence of abnormal combustion.

Audible spark kn0ck.-The octane number required to prevent spark knock was measured with the engine opcrating under the conditions specified above for surface ignition count. The number reported is the octane number of the lowest octane fuel which eliminated trace knock. Low values indicate improved performance.

Audible surface igniti0n.-The octane number required to prevent surface ignition was measured with the engine operating under the conditions set forth above for surface ignition count. The number reported is the octane numher of the lowest octane fuel which eliminated all significant audible surface ignition. Low values indicate improved performance.

Audible rumble.-The engine was operated at 2400 rpm. with a full throttle and the ignition timing set at 18 B.T.C. The data are reported as the number of the LIE reference fuel required to produce a trace intensity of rumble. The LIB number is the percent of iso-octane in benzene. Zero LIB is 100% benzene containing 3 ml. of TEL, and 100 LIB is 100% isooctane containing 3 ml. of TEL. A low LIB number indicates the deposits have a low tendency to cause rumble. At 100 hours 100 LIB fuel was not suflicient to prevent rumble with a wide open throttle. In these cases the engine was operated with 100 LIB fuel and the throttle was closed to the point of trace rumble. The rumble rating was then expressed as 100 LIB plus the maximum throttle tolerated expressed as intake manifold vacuum in inches of mercury. A low manifold vacuum indicates a large throttle opening tolerance, which is desirable for optimum engine performance.

The data obtained in these tests are set forth in the following table:

Hours Test Test Fuel Knock Rating:

no engine deposit modifier 2. 2 8. 0 tris (dibutorwphosphinylmethyl) phosphate 2. 4 3.8 Surface Ignition Count:

no engine deposit modifier 0 357 tris (dibutoxyphosphinylmethyl) phosphate 0 129 Audible Spark Knock:

no engine deposit modifier 100.7 105. 2 tris (dibutoxy'phosphinylmethyl) phosphate 101. 4 Audible Surface Ignition:

no engine deposit modifier 101.2 106. 4 tris (dibutoxyphosphinylmethyl) p sphate 101. 4 104. 2 Audible Rumble:

no engine deposit modifier 0 100+5.2 tris (dibutoxyphosphinylmethyl) phosphate 0 100+3. 5

1 Spark knock masked by surface ignition; values at 120 and 140 hour were 101.3 and 101.8, respectively.

While the compounds and compositions of this invention have been exemplified in such manner that one skilled in the art can readily understand and practice the invention, it should be understood that numerous other modifications and variations of the compositions described above may 'be made by those skilled in the art without departing from the spirit of the invention or the scope of the following claims.

I claim:

1. A tris(dibutoxyphosphinylmethyl) phosphate in which the butyl group is selected from the class consisting of n-butyl, isobutyl, and sec.-butyl.

2. Tris(di-n-butoxyphosphinylmethyl) phosphate.

3. Tris(diisobutoxyphosphinylmethyl) phosphate.

4. Tris(di-sec. butoxyphosphinylmethyl) phosphate.

5. The improved spark ignition fuel composition for internal combustion engines which comprises hydrocarbons of the gasoline boiling range containing a tris(dibutoxyphosphinylmethyD phosphate in which the butyl group is selected from the class consisting of n-butyl, isobutyl, and sec.-butyl in an amount suflicient to reduce abnormal combustion.

6. The improved spark ignition fuel composition for internal combustion engines which comprises hydrocarbons of the gasoline boiling range containing a tetraalkyl lead anti-knock agent and a tris(dibutoxyphosphinylmethyl) phosphate in which the butyl group is selected from the class consisting of n-butyl, isobutyl, and sec.-butyl in an amount sufficient to reduce abnormal combustion.

7. The improved spark ignition fuel composition for internal combustion engines which comprises hydrocarbons of the gasoline boiling range containing a tetraalkyllead antiknock agent and 0.01-0.5 theory of a tris(dibutoxyphosphinylmethyl) phosphate in which the butyl group is selected from the class consisting of n-butyl, isobutyl, and sec-butyl.

8. The improved spark ignition fuel composition of claim 7 in which the phosphate is tris(di-n-butoxyphosphinylmethyl) phosphate.

9. The improved spark ignition fuel composition of claim 7 in which the phosphate is tris(diisobutoxyphosphinylmethyl) phosphate.

10. The improved spark ignition fuel composition of claim 7 in which the phosphate is tris(di-sec.-butoxyphosphinylmethyl) phosphate.

References Cited in the file of this patent UNITED STATES PATENTS 2,632,767 Smith et a1 Mar. 24, 1953 2,897,071 Gilbert July 28, 1959 2,909,559 Lanham Oct. 20, 1959 2,948,599 Orlofi et al Aug. 9, 1960 

6. THE IMPROVED SPARK IGNITION FUEL COMPOSITION FOR INTERNAL COMBUSTION ENGINES WHICH COMPRISES HYDROCARBONS OF THE GASOLINE BOILING RANGE CONTAINING A TETRAALKYL LEAD ANTI-KNOCK AGENT AND A TRIS(DIBUTOXYPHOSPHINYLMETHYL) PHOSPHATE IN WHICH THE BUTYL GROUP IS SELECTED FROM THE CLASS CONSISTING OF N-BUTYL, ISOBUTYL, AND SEC-BUTYL IN AN AMOUNT SUFFICIENT TO REDUCE ABNORMAL COMBUSTION. 